Field of the Invention
The present invention relates to a brake device including independent left and right mechanisms, and relates to a technique for reducing an operating noise that occurs when a parking brake is actuated.
Description of Related Art
A brake device has been proposed in which an electric motor is used as a driving source to generate a braking force and the braking force can be maintained even after supply of electricity to the electric motor is stopped. In a vehicle on which this brake device is installed, an operating noise is generated when a parking brake is actuated, and this operating noise may cause an uncomfortable feeling or annoyance. Specific examples of such operating noises include a noise that is generated from a ratchet fitted in a pressure generating mechanism, a noise that is generated when a lock mechanism is locked, and a noise that is generated when a pressure that causes a braking force increases, and there is a demand to reduce an uncomfortable feeling or annoyance caused by such a noise.
Examples of methods for reducing the uncomfortable feeling or annoyance caused by an operating noise that occurs when the parking brake is actuated include a method to reduce the sound pressure level of the operating noise, and a method to reduce the likelihood that the noise will cause an uncomfortable feeling or annoyance. As an example of the first method, a method of optimizing the structures and configuration of a motor and a speed reducer (or a reduction gear) of an electric brake device equipped with an electric parking brake so as to reduce the operating noise has been proposed (Patent Document 1). In addition, in an electric parking device, since an impact that is made when an output shaft of a motor is locked causes an operating noise, a method of providing a projecting portion or a recessed portion of an engagement portion of a lock mechanism with an elastic portion to reduce the operating noise has been proposed (Patent Document 2).
As an example of the second method, there has been proposed a method of generating an electronic sound alerting an occupant of a vehicle from a start of an operation of a parking brake to an end thereof to notify the occupant of the operation of the brake, and, through the notification, impressing on the occupant the fact that an occurrence of an operating noise is a normal phenomenon due to the operation of the parking brake, thus allowing the occupant to feel at ease, and making it hard for the occupant to perceive any operating noise due to the electronic sound (Patent Document 3).